1. Field of the Invention
The present invention relates to so-called parabola type vehicular illumination lamps configured to form a light distribution pattern having a cut-off line at its upper end.
2. Description of the Related Art
Conventionally, in parabola type vehicular illumination lamps configured to reflect light from the light source forward by a reflector, the lamp configuration includes a shade that blocks light traveling downward from the light source so as to form a light distribution pattern that has a cut-off line at its upper end (e.g., a low-beam distribution pattern).
Japanese Patent Application Laid-Open (Kokai) No. 2003-288804 describes a parabola type vehicular illumination lamp that includes such a shade as described above, and in this lamp a translucent cover is provided in front of the reflector such that the translucent cover is inclined in the lateral direction, and part of reflected light from the reflector, which has been reflected by the translucent cover, is reflected outward in the lateral direction of a vehicle by a partial reflection area formed on the reflector.
The vehicular illumination lamp described in Japanese Patent Application Laid-Open (Kokai) No. 2003-288804 has the following problem. In this vehicular illumination lamp, not only the reflected light from the translucent cover but also the light directly emitted from the light source are incident on the partial reflection area of the reflector. Accordingly, if the vehicular illumination lamp is configured such that the partial reflection area reflects the reflected light from the translucent cover outward in the lateral direction of the vehicle, reflection control on the light directly emitted from the light source cannot be accurately performed, which affects formation of a light distribution pattern.
In parabola type vehicular illumination lamps, when an upper area of the translucent cover is inclined rearward, part of reflected light from the upper reflection area of the reflector is incident on the lower reflection area of the reflector after being reflected by the upper area of the translucent cover, depending on the inclination angle of the translucent cover, and since the light reflected by the lower reflection area includes light that travels upward, depending on the shape of a reflective surface thereof, this reflected light causes glare for oncoming drivers.
As a solution, the lower reflection area of the reflector can be configured to reflect the reflected light from the upper area of the translucent cover in a diffused manner, thus reducing glare for oncoming drivers.
However, even in this structure, it is not enough to effectively prevent glare for oncoming drivers, and light that is reflected by the upper area of the translucent cover and incident onto the lower reflection area of the reflector cannot be used effectively.